Did not having suffered a reduction to their population effect power dynamics in the region?
Did Poland forego the 'positives' of black death such as an increase in wages due to labour shortages?
Was their any significant migration of Poles to neighbouring regions?
The assumption that Poland has not suffered during the outbreaks of bubonic plague in 14th century is based on a popular but substandard research in the 1960s (there are few Polish sources of the event but absence of evidence is not an evidence of absence) that has been rectified quite thoroughly since then. You might be interested in this excellent response by u/mikedash that addresses several issues related to the ways Black Death affected Poland and neighbouring regions.